and some of them are well-known fragrants found in the essential oils of many plants. For example, camphor, citral, citronellol, geraniol, grapefruit mercaptan, eucalyptol, ocimene, myrcene, limonene, linalool, menthol, camphene and pinenes are used in perfumes and cosmetic products. Limonene and perillyl alcohol are used in cleaning products. Many monoterpenes are used as food flavors and food additives, such as bornyl acetate, citral, eucalyptol, menthol, hinokitiol, camphene and limonene. Menthol, hinokitiol and thymol are also used in oral hygiene products. Thymol also has antiseptic and disinfectant properties. Volatile monoterpenes produced by plants can attract or repel insects, thus some of them are used in insect repellents, such as citronellol, eucalyptol, limonene, linalool, hinokitiol, menthol and thymol. Ascaridole, camphor and eucalyptol are monoterpenes that have pharmaceutical use. Health effects A study suggests that a range of floor cleaners with certain monoterpenes may cause indoor air pollution equivalent or exceeding the harm to respiratory tracts when the time is spent near a busy road. This is due to ozonolysis of monoterpenes like Limonene leading to the production of atmospheric SOA. Another study suggests monoterpenes substantially affect ambient organic aerosol with uncertainties regarding environmental impacts. In a review, scientists concluded that they hope that these "substances will be extensively studied and used in more and more in medicine". A 2013 study found that "Based on adverse effects and risk assessments, d-limonene may be regarded as a safe ingredient. However, the potential occurrence of skin irritation necessitates regulation of this chemical as an ingredient in cosmetics." According to a review, several studies showed "that some monoterpenes (e.g., pulegone, menthofuran, camphor, and limonene) and sesquiterpenes (e.g., zederone, germacrone) exhibited liver toxicity" and that i.a. intensive research on terpenes toxicity is needed. See also Terpene Terpenoid Diterpene Sesquiterpene References Monoterpenes Terpenes and terpenoids